Exploring novel fluorine-rich fuberidazole derivatives as hypoxic cancer inhibitors: Design, synthesis, pharmacokinetics, molecular docking, and DFT evaluations

Sixteen fuberidazole derivatives as potential new anticancer bioreductive prodrugs were prepared and characterized. The in vitro anticancer potential was examined to explore their cytotoxic properties by employing apoptosis, DNA damage, and proliferation tests on chosen hypoxic cancer cells. Eight substances (Compound 5a, 5c, 5d, 5e, 5g, 5h, 5i, and 5m) showed promising cytotoxicity values compared to the standard control. The potential of compounds was also examined through in silico studies (against human serum albumin), including chem-informatics, to understand the structure-activity relationship (SAR), pharmacochemical strength, and the mode of interactions responsible for their action. The DFT calculations revealed that only the 5b compound showed the lowest ΔET (2.29 eV) while 5i showed relatively highest βtot (69.89 x 10–31 esu), highest αave (3.18 x 10–23 esu), and dipole moment (6.49 Debye). This study presents a novel class of fuberidazole derivatives with selectivity toward hypoxic cancer cells.


Introduction
Hypoxia plays a vital role in cancer cell survival against cancer therapy. Cancer cells show different cellular biological activities and reactive oxygen species (ROS) levels due to higher metabolic activity [1]. A high level of ROS disrupts mitochondrial function. The hypoxia condition is referred to the less oxygen supply at the tissue level, and cancer cells show increased a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 analytical procedures. The melting points were determined using Gallon Kamp's melting point instrument. The 1 H NMR (300 MHz) and 13 C NMR (75.43 MHz) spectra were collected on a Bruker AM-250 spectrometer utilizing CDCl 3 and DMSO as internal standards. A UV-Visible spectrophotometer was used to obtain UV-Visible absorption spectra, model UV-1700. Elements were analyzed using a Leco CHNS-932 Elemental Analyzer (Leco Corporation, USA).

General method for the compounds (5a-p) synthesis
In the first step, the halo substituted furfural (10 mmol) was added to a stirred solution of 4,5,6-tri-fluorobenzene-1,2-diamine (10 mmol) in a more environmentally friendly solvent polyethylene glycol (PEG 400 ). The reaction mixture was heated at an elevated temperature of 80-85˚C. TLC was used to monitor the reaction progress. Following aqueous workup, the crude product was obtained and refined with a mobile phase of hexane: ethyl acetate to get the pure compound (3a-3d). In the second step, the compound 3a-3d (10 mmol) was stirred with equimolar NaH in acetone for one hour. After one hour, the appropriate alkyl halide (10 mmol) was added to the mixture and agitated for five hours at room temperature. TLC has also been used for monitoring the reaction progress. After the reaction, the organic extract was prepared by dissolving the reaction mixture in water and extracting it with dichloromethane (3×100 mL). The organic extract was dried in the presence of anhydrous sodium sulphate and then imaged by chromatography over silica gel using ethyl acetate: petroleum ether (1:1) as the eluting system to obtain pure fuberidazole (5a-5p) as a pure product. Following fuberidazole, derivatives were obtained by using the above procedure.

Biochemistry experiments
Antioxidant activity. The in-vitro antioxidant free radical scavenging potential of the fuberidazole derivatives (5a-5p) was assessed utilizing a reduction method DPPH (2,2-diphenyl-1-picryl hydrazyl) with the slightly modified protocol [21,22]. The stock methanolic solution of DPPH was prepared (4 mg DPPH/4 mL MeOH) and further dilutions were also prepared at concentrations: 1.0, 2.0, 4.0, 8.0, 16.0, 32.0, 64.0, 128, 256, and 500 μg/mL. At 517 nm, the absorbance of sample solutions was determined. All sample solutions were produced and stored in the amber reagent bottle. As a positive control, tert-butyl-1-hydroxytoluene (BHT) was produced by dissolving 2 mg of BHT in methanol to obtain a mother solution (1000 μg/mL). The methanolic solutions of compounds 5a-5p (2 mg each) were prepared to get a stock solution of 1000 μg/mL concentration. The serial dilution method was used to prepare test samples from this stock solution using methanol to attain the concentration ranges like DPPH. A 2.0 mL test compounds solution and 3.0 mL of DPPH solution (20μg/mL) were mixed, followed by vigorous shaking, and then kept undisturbed in a dark place for 30 minutes at ambient temperature. The absorbance at 517 nm has been determined by employing methanol as a standard using a UV-Spectrophotometer. The fraction of the inhibited free radical DPPH was estimated utilizing the following equation: Where A blank refers to the control reaction absorbance.

WST cytotoxic assay
MCF-7 cells were exposed to a varied concentration of the vehicle (0.2% DMSO) or the synthesized compound (500 to 1 μM solution of DMSO) for control cells. After 48 hours of incubation with the examined drugs, the cell viability was determined using the WST-1 assay (Millipore) [24]. In this assay, cellular mitochondrial dehydrogenase changed the tetrazolium salt WST-1 to formazan dye, whose concentration correlates with the viable cell in the culture. The absorbance at 440 nm was determined using a BioTek Synergy H1 plate reader (BioTek, Winooski, VT; USA). The percentage of viable cells was calculated using the following formula.
% viable cells ¼ absorbance of test absorbance of control X 100

DNA damage assay
The DNA-damaging effect of the substances was assessed using the EpiQuick in situ assay kit, which quantifies histone (H2AX) phosphorylation on serine 139. Seeding of A549/WM115 cells was carried out in 96-well plates at a concentration of 5000 cells / well and allowed for subsequent culturing under hypoxic conditions for 24 h before treatment. Subsequently, at the same culture conditions, the compounds were used to treat the cells/vehicles at concentrations ranging from 1C 50 at the same culturing conditions. The DNA-damaging effect in the hypoxic cells was determined 4 hours after incubation, followed by fixation of cells and assay performance according to protocol. The DNA damage and intensity of color development in the samples were proportional. On a Synergy-H1 plate reader, the absorbance of the samples was determined at 430 nm. The damaged fraction of DNA was determined using the following expression: The optical density of samples is a measure of the absorbance of cells treated with test and control substances, as well as the optical density of the vehicle-treated control cells in the absence of test compounds.

Apoptosis assay
This technique is based on using a proluminescent substrate containing DEVD to determine caspase-3/7 activity (Z-DEVD-aminoluciferin). Caspase Glo 3/7 assay [Promega] was employed based on the manufacturer's instructions. Caspase cleavage liberates a resource for luciferase, which catalyzes the luciferase reaction and generates a bright signal. Caspase 3/7 activity was determined in hypoxic MCF-7 cells after 4, 24, and 48 h of treatment with the tested drugs. The luminescence at gain 135 was measured using a Synergy H1 and a Bio-Tek microplate reader [25].

Computational methodology
Properties of produced compounds based on chemo-informatics and ADMET. The cheminformatics and biological parameters of synthesized compounds (5a-5p) were calculated by online servers, such as Molsoft and Molinspiration. Molinspiration was also used to observe the implication of Lipinski's rule of five. Additionally, their ADMET properties were analyzed using the pkCSM online tool.
When an isolated molecule is exposed to an incident electromagnetic wave's applied electric field (E), microscopic polarizability may be produced in that molecule, the magnitude of which can be expressed as follows: Where P and E represent tensor quantities, while α and β represent polarizability and hyperpolarizability, respectively.
Moreover, the average dipole moment (μ) can be defined in Eq (2) The polarizability (α) of a molecule can be defined as in Eq (3) The anisotropy of polarizability is: Eq (5) can be used to compute the components of first-order hyperpolarizability.
The first-order hyperpolarizability is a tensor component of the third rank, which can be explained by a 3 x 3 x 3 matrix [36]. Then, the magnitude of the first hyperpolarizability can be determined using x, y, and z components as in Eqs (6) and (7).
Statistical analysis of the data. For statistical analysis, the student's t-test was utilized. The significance level was set at the value of 0.05. The results are provided as mean and standard deviation (± S.D.).

Chemistry
To synthesize fuberidazole derivatives 5a-5p, a facile and green route was adopted in which 3,4,5-trifluorobenzene-1,2-diamine 1 was treated with furan-2-carbaldehyde derivatives 2 using PEG 400 as a greener medium giving intermediate 3a-3d confirmed by elemental analysis and 1 H and 13 C NMR (see S1 Table, S1-S40 Figs in S1 File). The intermediate 3a-3d were then reacted with RCl 4 and sodium hydride in the presence of a minimum quantity of acetone as a solvent for five hours at room temperature, which afforded fuberidazole derivatives 5a-5p in good to excellent yields (Scheme 1). Some by-products were also obtained other than the desired product. Therefore, we purified them by preparative TLC and column chromatography. The structures of 5a-5p were assigned according to multinuclear ( 1 H and 13 C NMR) and PLOS ONE CHN analysis. In the 1 H NMR spectra of 5a-5p, the down-field singlets in the region 11.49-11.00 ppm were assigned to the N.H. ring proton. The peaks that appeared in the range 3.75-1.55 ppm are linked with -CH 2 and -CH 3 groups present in their respective compounds. All the aromatic protons of benzene moiety resonated between 7.45-6.25 ppm. A peak of one proton attached with carbon linked to the oxygen of furan moiety resonated downfield in the range of 7.87-7.46 ppm. 13 C NMR spectral study of fuberidazole and its derivatives using chemical shift principal has been taken. The effect of substitution at imidazolic nitrogen and furan ring on the chemical shift values of all the carbons of the fuberidazole molecule is discussed. It is seen that the carbon of furan (C-1) attached to the imidazole ring showed maximum downfield shift ranging from 159.7 ppm to 154.0 ppm. In contrast, carbon (C-8) of benzene resonates at the second-highest downfield shift in C-13 spectra. The imidazolic carbon (C-5) appeared in the range of 138.2 ppm to 147.5 ppm. The alkyl substitution of the nitrogen atom has little shielding and deshielding effect on other carbon atoms, resulting in the close range in chemical shift values of the carbon atoms in the fuberidazole derivative. Further confirmation has been made based on CHN analyses. The values are within limits of ± 0.3%.

Biological activities
DPPH radical scavenging activity. The antioxidant potential was assessed using DPPH radical scavenging protocol having Butylated hydroxytoluene (BHT) as a positive control. The potential of the compound was determined by determining its electron-donating capacity toward DPPH, as shown by variations in the absorbance of a fluid of varying concentrations at 517 nm. The activity of DPPH radical scavenging of the fuberidazole derivatives' is linearly elevated with concentration. The findings on radical scavenging were described as the half-inhibition concentration (IC 50 ), which is defined as the concentration which is necessary to scavenge 50% of DPPH radicals (Fig 1).
Fuberidazole derivatives 5a and 5e showed IC 50 of 1.023 and 1.04 μg /mL, respectively, which seemed to be very promising and could be due to the presence of the halo group, which generally gives considerable biological activity. Concerning alkyl substituents, going to i-Pr from H-over CH 3 , and Et, quite a significant amount of compound is needed to show IC 50 activity. Therefore, compounds substituted with H-atom (5a, 5e, 5I, 5m) showed better results than others. On the other hand, all fuberidazole derivatives (5a-5p) exhibited mild to prominent antioxidant activity (18.67-1.023 μg /mL) because of the halogen substitution or the N atom, which is a crucial atom in many drug candidate molecules.
Effect of compounds on cell proliferation of MCF-7 cells. We estimated the potential of synthesized fuberidazole derivatives on hypoxic MCF-7 cells. As revealed in Fig 2, compounds  5a, 5e, 5h, and 5i demonstrated the highest activity among the synthesized compounds (5a-5p) in hypoxic conditions when compared to the hypoxic drug tirapazamine. The compound 5a proved to be most active among 5a-5p against hypoxic cells, while the compound 5n exhibited an inactive action. The exposure of hypoxic cells to 5a at a concentration of ca. 100 μM resulted in an 80% reduction in cell survival. In contrast, compounds 5e and 5h showed cell survival of 53 and 56%, respectively, at the same concentrations. The 5n, 5o, and 5p have no obvious anticancer potential at any concentrations examined in hypoxic cells (Figs 2 and 3).
Based on the results of the viability of hypoxic cells, the compounds (5a, 5c-5e, 5g-5i, 5m) are highly active and selected for further testing.
Potential of compounds 5a-5p on DNA damage in hypoxic MCF-7 cells. In this regard, we calculated the phosphorylation of H2AX at Ser139 in hypoxic MCF-7 cells by exposing them for 4 h to the chosen compounds, tirapazamine, and etoposide, at the IC 50 concentrations. The hypoxic cancer cells treatment with fuberidazole derivatives 5g, 5i, and 5m results in improved H2AX phosphorylation levels (Fig 4). Compound 5m had the highest efficiency and enlarged the DNA damage by 1.5-fold in hypoxic cells compared to the control. In the treatment of the hypoxic cells with the fuberidazole derivatives 5d and 5h, the DNA damage was equivalent to that observed in control cells. Conversely, 5a had no discernible effect on H2AX phosphorylation. Additionally, hypoxic cells exposed to tirapazamine caused DNA damage by 1.8-fold more than control cells. Because of these findings, we can conclude that compounds 5g, 5i, and 5m induced DNA damage in hypoxic MCF-7 cells at concentrations in the IC 50 range.
Potential of compounds on cell apoptosis. We selected compounds (5a, 5c-5e, 5g-5I, and 5m) for apoptotic activity using the IC 50 values of fuberidazole derivatives. The activity of caspase 3/7 was investigated to assess the impact of apoptosis in the inhibition of hypoxic MCF-7 cell growth. Apoptosis assays were done in hypoxic MCF-7 cells treated with compounds (5a, 5c-5e, 5g-5I, and 5m) at IC 50 concentrations for different intervals. After 24 and

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48 h, no elevation in the activity of caspase 3/7 was observed when hypoxic cells were treated with chemicals (5a, 5c-5e, 5g-5I, and 5m) relative to control. In comparison, the treatment of hypoxic cells with tirapazamine for 24 h raised caspase 3/7 activity by seven times, while treating them for 48 h doubled its activity (Fig 5). The results indicated that the synthesized compounds (5a, 5c-5e, 5g-5I, and 5m) inhibited MCF-7 cell growth rather than cell proliferation at the tested concentrations.
A plausible structure-activity relationship of active fuberidazole derivatives. In the fuberidazole derivatives under investigation, the leading pharmacophore group comprises the

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Fuberidazole derivatives as hypoxic cancer inhibitors benzimidazole moiety as an essential receptor. The N-H group in imidazole may act as a binding site for the receptor. The presence of electron-withdrawing substituents to the adjacent furan ring's meta-position could enhance the overall biological activity. In this regard, substituents F-, Cl-, Br-, and I-were used to investigate their effect on pharmacological properties. The SAR is wisely explained in Fig 6. Chemo-informatics properties and Lipinski's rule of compounds (5a-5p). The chemoinformatics characteristics of compounds (5a-5p), such as molecular weight, LogP, PSA, and molecular volume, were calculated and assessed by using computational methodologies listed in Table 1. The results confirmed that molecular weight (g/mol), molar volume (A 3 ), and polar surface area (A 2 ) of compounds 5a-5p were correctly computed. All the calculated values for these substances were performed to agree with the PSA (<89 A 2 ) [37] standard value.

Fig 4. Effect of selected fuberidazole derivatives on DNA damage in hypoxic MCF-7 cells, CTR (control), E (etoposide), and T (tirapazamine).
The control sample (CTR) included MCF-7 cells that had not been exposed to the substances under study. Statistical data: mean and standard deviation of trials are represented as n = 3.
https://doi.org/10.1371/journal.pone.0262790.g005 Furthermore, the results of Lipinski's rule of five (RO5) indicated that (5a-5p) compounds had appropriate HBD and HBA values, which substantially supported their drug-like activity. All compounds had molecular weights that were very similar to the standard limit (< 500 g/ mol). The RO5 showed that molecules with low absorption have an HBD value of more than five, MWT was more significant than 500, a logP higher than 5, and an HBA value of more than 10.
Pharmacokinetic properties of fuberidazole derivatives (5a-5p). The pharmacokinetics characteristics, such as Distribution, Metabolism, Absorption, and Toxicity (ADMET), Excretion, and estimation, are thought to be the principal characteristics used to validate the efficiency of compounds. The ADMET properties of compounds have been calculated through the pkCSM online server ( Table 2). It is stated that compounds with high absorption potential quickly attack the target molecule by passively penetrating (crossing) the gut barrier [37]. All compounds (5a-5p) are highly water-soluble (W.S.) and exhibit a high intestinal absorbance (I.A.) when compared to the standard value (>30% abs). According to reports [38], a substance having an absorbance value of less than 30% is regarded to be poorly absorbed. Since all compounds have higher skin permeability (S.P.) values than the standard value (−2.5 log Kp) strongly recommended that they exhibit drug-like behavior. Moreover, the Central Nervous System (CNS) permeability and Blood-Brain Barrier (BBB) values of all compounds were  within the normal range (>−2 to <−3 logPS and >0.3 to <−1 log B.B.), respectively. Only substances with a value larger than 0.3 log BBB pass across the BBB, but those with less than −1 values are poorly dispersed to the brain. Likely, the substances with the LogPS values greater than −2 can penetrate the CNS, but those with a value less than −3 have difficulty spreading across the CNS. The compounds examined in this research displayed a high capability for crossing these barriers and binding to receptor molecules. The synthesized compound can inhibit the CYP3A4 enzyme (the isoform of cytochrome P450). The anticipated toxicity and excretion values indicated that these compounds exhibit the drugs-like behavior based on AMES toxicity, LD 50, maximum tolerated dose (MTD), and log ml/min/kg values. Additionally, the nontoxic and non-mutagenic behavior was evaluated using AMES toxicity prediction. Both negative and positive hepatotoxic behavior showed less sensitive and toxic effects. Most of the compounds displayed skin sensitizer and hepatotoxic properties. The ADMET properties results validated the perspective of these synthesized compounds to perform as lead compounds with minimal skin sensitivity and hepatotoxicity.
Molecular docking. The interaction pattern was investigated using molecular docking, by which the optimal conformation of the fuberidazole derivatives in the target protein's active site was determined, and the inhibitory efficacy against the target protein was assessed. Fig 7  illustrates the binding affinity score for inhibitors. All the inhibitors were docked in the proximity of the known active site (around the coordinates of TRP214). The AutoDock program was used to evaluate the optimum conformational position of the synthesized substances against human serum albumin (PDB code: 1AO6). The bonding interaction pattern (hydrogen/hydrophobic) and minimum binding affinity values (kcal/mol) were used to evaluate the resultant docked complexes. Docking results discovered that 5e exhibited the lowest value of binding affinity (-8.1 kcal/mol), while 5p predicted the binding affinity of -0.4 kcal/mol, which was found to be higher than the rest of the synthesized compounds. The supplemental data provide a list of all fuberidazole derivatives having docked complexes (S41-S56 Figs in S1 File).
The docked complex was then analyzed further using hydrogen bonding, π-Alkyl, π-anion, π-Sulfur, π-sigma, and Van der Waals interactions. Docking analysis demonstrated that all

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docked substances interacted with the active binding area of human serum albumin [30]. On the other hand, compound 5e had the lowest binding affinity (-8.1 kcal/mol) and the best fit into the active pocket of human serum albumin. As seen in the 3D and 2D images of compounds 5e and 5g (Figs 8 and 9), hydrogen bonding and hydrophobic interactions dominate the interaction between the formed substances and the target protein (Figs 10 and 11). ARG 222 from the active pocket of the protein has been observed to form hydrogen bonds. It is noted from the data that the residues ILE290, LEU 219, TYR150, HIS242, LYS199, LEU238, and ALA291 have been involved in hydrophobic interactions in the protein-ligand complex. Compound 5e also exhibited Van-der-Waal interactions with the human serum albumin. Docking results revealed that the compound 5g was tightly bonded to the active site of the human serum albumin (binding affinity -7.9 kcal/mol) and established three ordinary hydrogen bonds with PRO C:303, PRO C:306, and GLU C:314. Van-der-Waal interactions were observed by 5g with several amino acid residues in the binding pocket of human serum albumin. Overall, the docking study determines the reported compounds' high affinity for human serum albumin (PDB code: 1AO6), indicating that they might be regarded as potent suppressors in future drug discovery.

DFT analysis
At the (U)B3LYP/6-311+G(d,p) level, the optoelectronic and first-order NLO response properties of a series of fuberidazole derivatives 5a-5p (Scheme 1) with different substituents at the  N-atom of imidazole ring (-H, -Me, -Et, and -i-Pr) and the 3-position of furan ring (-F, -Cl, and-Br), respectively. We first discuss triplet energies and HOMO-LUMO gaps. Secondly, dipole moments, polarizabilities, and first-order hyperpolarizabilities are discussed. Finally, NBO analysis is carried out to investigate the donor-acceptor interaction.
Triplet energies. Quantum chemical calculations of the gas-phase triplet energies revealed that all fuberidazole derivatives (5a-5d) have lower triplet energy than their bromoand chloro-substituted ones (Fig 12). This could be interpreted as fluorination having the effect of lowering the triplet energy. Bromo-substituted compounds (5i-5l) display the highest triplet energies. In the case of alkyl substituents on the N-atom of the imidazole unit, methylsubstituted compounds (5b, 5f, 5j, and 5n) showed the lowest triplet energies within each series. The triplet energies have been increased when going from methyl to isopropyl over ethyl substituent, which could be due to the steric repulsion. The increase in the steric bulk at the N-atom of the imidazole unit reduces the planarity of the compound, which weakens πconjugation and increases triplet energy. Interestingly, compound 5b showed the lowest triplet energy (2.29 eV). However, when the imidazole moiety's benzene ring and furan ring are unsubstituted, the triplet energy is 2.38 eV, which is significantly higher than that of substituted compounds. Introducing electron-donating substituents (alkyl groups) on the N-atom of the imidazole (acceptor site), at the same time, introducing electron-withdrawing substituents on the furan ring (donor side) leads to a significant decrease in triplet energies. In summary, with proper choice of the electron-donating substituent on the acceptor unit and electronwithdrawing substituent on the donor unit, it could be possible to control the triplet energies of this series of compounds, possibly due to the push-pull effect.
HOMO-LUMO energy gaps. The electronic, optical, and spectroscopic properties of fuberidazole derivatives can be analyzed with the help of frontier molecular orbitals (FMOs). FMOs are also a form of electrical conductivity and can provide information about intramolecular charge transfer. The lower the HOMO-LUMO energy gap, the greater the probability of charge transfer. The results of the orbital analysis showed that HOMO-LUMO gaps for all compounds range from 4.88-4.33 eV (Fig 13). The smallest ΔE H-L is found for compound 5a (4.33 eV). However, the energies of HOMO and LUMO are not significantly affected by changing the substituents. The excitation is mainly ππ � .
Dipole moments. The molecular dipole moments are used to indicate the charge transport along the molecule [39]. The gas-phase calculated dipole moments range from 5.54-6.49 Debye (Fig 14). Interestingly, dipole moments increased when the electronegativity of the halogen atom decreased at the furan unit. In addition, a significant increase in dipole moments is observed by changing the substituent on the N-atom. The highest dipole moment is observed for 5l and the lowest for 5a.
Polarizability and first-order hyperpolarizabilities. The polarizability refers to the magnitude of electron density distortion and responsiveness of a system when a static electric field is applied externally. It was reported that substantial values of hyperpolarizability are a crucial requirement for a molecule to be a good NLO material. The polarizability (α ave ) and firstorder hyperpolarizability (β tot ) showed a similar trend to what was observed for the dipole moment. Both above properties decrease with increasing the electronegativity of the halogen atom and increase with the introduction of the bulky electron-donating alkyl substituent at the N-atom [40]. This can be explained as electron-donating groups increasing the induced ring current, which can then be responsible for the enhanced NLO response. However, the effect of substituents on α ave is less pronounced. The α ave range from 2.37-3.18 x 10 −23 esu and β tot range from 49.11-69.89 x 10 −31 esu. The highest value of α ave and β tot is observed for 5l. The results support the hypothesis that polarizability and first-order hyperpolarizabilities can be tuned by changing the substituents on the donor and the acceptor units (Fig 15). Moreover, these fuberidazole derivatives could potentially be good candidates for NLO applications. Natural bond orbital (NBO) analysis. The natural bond orbital (NBO) method of Weinhold provides information about the interaction within the different parts of the molecules, namely donor and acceptor units [41]. The charges on different sites of the molecule were calculated by NBO to analyze the donor-acceptor interaction in the molecule. In fuberidazole, the benzimidazole unit, when substituted with electron-donating groups, is known to act as an acceptor moiety in push-pull chromophores [42,43]. Our results show similar results as the benzimidazole unit acting as an acceptor and the furan unit acting as a donor in fuberidazole (Fig 16). The strong donor-acceptor push-pull interaction is observed in 5l among the series of compounds, which might be responsible for increased α ave and β tot values.
A thought to extend conjugation by π-bridge. As it is known that the NLO response of materials can be enhanced by placing a π-bridge in between the donor and acceptor units [44]. We designed three compounds with different π-bridges and calculated α ave and β tot for them at the B3LYP/6-311+G(d,p) level. It is found that when the C = N bridge is placed, a significant enhancement in β tot is observed. On the other hand, when benzene is inserted as a π-bridge, no improvement in β tot is observed. This reflected that the benzimidazole unit is separated by a πbridge with a furan unit, which could display significantly enhanced NLO response characteristics. However, these compounds are only designed computationally (Fig 17). In the future, we have a plan to synthesize and investigate the practical applications of synthesized compounds.

Conclusion
The biochemical research conducted in this study enabled us to establish certain conclusions regarding the biological impacts of fuberidazoles. We have described the synthesis, in-vitro, and in silico screening of sixteen fuberidazole derivatives as potential new anticancer candidates. All compounds showed mild to prominent antioxidant activity, but few (5a, 5e, 5I, and 5m) showed better results than others. The in-vitro anticancer potential, apoptosis, proliferation, and DNA destruction experiments on selected hypoxic cancer cells were also described. Out of sixteen, eight compounds (5a, 5c, 5d, 5e, 5g, 5h, 5i, 5m) displayed good cytotoxic properties. This moderate relation between antioxidant and anticancer activities of tested substances implies that anticancer activity in the examined MCF-7 cells may be attributed to their antioxidant properties. SAR, pharmacochemical strength and the mode of interactions responsible for the activity have also been examined via in silico studies (against human serum albumin) using chem-informatics. Furthermore, molecular docking research was also conducted to calculate binding energy and protein interaction. Our docking studies established the described compounds' high affinity for human serum albumin (PDB code: 1AO6). As a result, these molecules may be regarded powerful inhibitors throughout the drug development process in the future. Finally, our results of quantum chemical calculations show that the most electronegative F atom and least bulky alkyl groups at the acceptor and the donor sides, respectively, can decrease the triplet energies. It is found that the least electronegative atom and the bulkiest electron-donating substituent on the donor and the acceptor sides, respectively, show relatively highest values for β tot (69.89 x 10 −31 esu), α ave (3.18 x 10 −23 esu), and dipole moment (6.49 Debye). The compound 5l showed the best results among the series of compounds. The donor-acceptor sites were also identified by the NBO analysis. Therefore, depending on the choice of application, one can tune the optoelectronic properties by properly placing substituents on the donor and the acceptor units. Noteworthy, the nonlinear response characteristics of compounds (5a-5p) are investigated only; theoretically, one needs to confirm these results experimentally because these compounds could potentially be used as future organic linear and NLO materials.